The equipment for the gas turbine such as the combustor liner, turbine blade, heat exchanger, fin, boiler, and heating furnace has been designed to be variously configured based on the specification required to satisfy the heat transfer enhancement between fluid and solid in the processes of cooling, heating and heat exchange. For example, the combustor used in the gas turbine for generation is required to maintain necessary cooling performance with small pressure loss not to deteriorate the gas turbine efficiency as well as to maintain reliability in the structural strength.
Furthermore, reduction in emission of nitrogen oxide (NOx) generated in the combustor is demanded to cope with environmental issues. Generation of NOx may be attributed to the fact that oxygen and nitrogen contained in air are kept at the significantly high temperature during combustion. In order to reduce the NOx by solving the above-described problem, the premixed combustion is implemented by mixing the fuel and air before combustion and combusting the mixture at the fuel-air mixture ratio (fuel-air ratio) lower than the stoichiometric ratio.
JP 2001-280154 discloses an example of the gas turbine combustor in consideration of the aforementioned requirements. According to JP 2001-280154, the plate-like longitudinal vortex generator and the rib-like turbulator are formed on the outer surface of the combustor liner to improve the cooling performance with small pressure loss. The gas turbine combustor in JP 2001-280154 includes a liner formed by axially connecting plural cylindrical members each derived from rounding substantially rectangular plate material into a cylindrical shape. The respective cylindrical members of the liner are connected with one another in the state where the adjacent cylindrical members are overlapped. The overlapped parts are bonded by welding. One end (downstream side in the flow direction of the compressed air from the compressor) of the cylindrical member is provided with plural protruding portions (longitudinal vortex generator) formed through press machining along the circumferential direction. The longitudinal vortex generator generates the longitudinal vortex having the center axis of rotation directed to the flow of the heat transfer medium (the compressed air) to agitate the flow passage of the heat transfer medium by the longitudinal vortex. Furthermore, the outer peripheral surface of the combustor liner is provided with a rib (turbulator) for destroying the boundary layer generated in the heat transfer medium agitated by the longitudinal vortex generator. The rib is formed through machining, welding or centrifugal casting.
JP 6-221562 discloses a gas turbine combustor as another example of the heat transfer structure, which includes a flow sleeve (outer duct) outside the liner for the purpose of forming the flow passage of the cooling air (heat transfer medium). The internal diameter of the flow sleeve is gradually reduced along the flow direction of the heat transfer medium. The gas turbine combustor in JP 6-221562 is configured to increase the flow velocity of the heat transfer medium by narrowing the flow passage of the heat transfer medium between the liner and the flow sleeve, and to improve the heat transfer coefficient by increasing the surface roughness of the liner surface.
JP 2000-320837 discloses a gas turbine combustor as another example of the heat transfer structure, which includes guide fins at the outer peripheral side of the liner and the inner peripheral side of the flow sleeve so that the heat transfer effect is improved by increasing the flow velocity of the compressed air (heat transfer medium). The gas turbine combustor in JP 2000-320837 is configured to reduce the cross section area of the annular flow passage formed between the combustor liner and the flow sleeve by the guide fins to improve the heat transfer effect by increasing the flow velocity of the heat transfer medium flowing through the annular flow passage.
The gas turbine combustor disclosed in JP 2001-280154 is superior to conventional combustors in the cooling performance and low NOx, but still has a problem to be solved with respect to the structural strength, simplicity in the manufacturing process, and the long service life. For example, the combustor liner is formed by connecting plural cylindrical members in an axial direction and the overlapped parts between the cylindrical members are bonded by welding, which may cause cracks and impede the long-term use compared with the case where the welding is not applied (that is, the single cylindrical member is used for forming the liner). As the number of the welded points is increased, the number of the manufacturing process steps is also increased, thus leading to the manufacturing cost increase. This may become more marked when the rib as the turbulator is fixed by welding. Furthermore, the welding will thermally deform the respective cylindrical members, deteriorating the incorporation of other circular members (for example, a circular plate to which the fuel nozzle or the premixing nozzle is attached, and the transition piece (tail duct)) into the combustor liner, which necessitates a process for forming the liner into the circular shape again. This may cause the risk of complicating the process for manufacturing the combustor. The overlapped part between the respective cylindrical members for forming the liner has a two-layer structure with thickness larger than that of the other part. This may degrade the heat transfer performance (coolability) of the overlapped part compared with the other part.
The gas turbine combustor disclosed in JP 6-221562 has a simply structured liner compared with the gas turbine combustor in JP 2001-280154. It is therefore superior in simplicity of the manufacturing process and the long service life. The heat transfer performance of the combustor of JP 6-221562 is enhanced only by increasing the flow velocity of the heat transfer medium and the surface roughness of the liner surface. As a result, the combustor of JP 6-221562 has a problem to be solved that the pressure loss is inevitably increased to obtain significantly high heat transfer enhancing effect (cooling effect). As the flow passage for the cooling air is gradually narrowed toward the burner, the highest cooling effect is obtained near the burner. If high temperature section of the combustor liner is located at a position away from the burner, the combustor of JP 6-221562 cannot cool the high temperature section sufficiently.
The gas turbine combustor disclosed in JP 2000-320837, having a guide fin disposed at the inner peripheral side of the flow sleeve, is superior in simplicity and long service life. However, the heat transfer (cooling) performance is enhanced only by increasing the flow velocity of the heat transfer medium. Therefore, the combustor of JP 2000-320837 has a problem that the pressure loss is inevitably increased to obtain significantly great effect of enhancing the heat transfer, just like the combustor of JP 6-221562.
An object of the present invention is to provide a gas turbine combustor configured to enhance the cooling of the combustor liner with suppressing increase in the pressure loss, and to have advantageous effects of excelling in the structural strength, simplicity of the manufacturing process, and long service life.